Open AccessComparative Analysis of Chromatin Binding by Sex Comb on Midleg (SCM) and Other Polycomb Group Repressors at a Drosophila Hox Gene
Author(s) -
Liangjun Wang,
Neal Jahren,
E. L. Miller,
Carrie S. Ketel,
Daniel R. Mallin,
John Simon
Publication year - 2010
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.01451-09
Subject(s) - prc2 , biology , chromatin , polycomb group proteins , genetics , chromatin immunoprecipitation , gene knockdown , hox gene , ultrabithorax , gene silencing , repressor , microbiology and biotechnology , gene , histone h3 , gene expression , promoter
Sex Comb on Midleg (SCM) is a transcriptional repressor in the Polycomb group (PcG), but its molecular role in PcG silencing is not known. Although SCM can interact with Polycomb repressive complex 1 (PRC1)in vitro , biochemical studies have indicated that SCM is not a core constituent of PRC1 or PRC2. Nevertheless, SCM is just as critical forDrosophila Hox gene silencing as canonical subunits of these well-characterized PcG complexes. To address functional relationships between SCM and other PcG components, we have performed chromatin immunoprecipitation studies using culturedDrosophila Schneider line 2 (S2) cells and larval imaginal discs. We find that SCM associates with a Polycomb response element (PRE) upstream of theUbx gene which also binds PRC1, PRC2, and the DNA-binding PcG protein Pleiohomeotic (PHO). However, SCM is retained at thisUbx PRE despite genetic disruption or knockdown of PHO, PRC1, or PRC2, suggesting that SCM chromatin targeting does not require prior association of these other PcG components. Chromatin immunoprecipitations (IPs) to test the consequences of SCM genetic disruption or knockdown revealed that PHO association is unaffected, but reduced levels of PRE-bound PRC2 and PRC1 were observed. We discuss these results in light of current models for recruitment of PcG complexes to chromatin targets.